Additional Pathways of S-Conjugate Formation during Interaction of 4-Nitrosophenetole with Glutathione

Abstract

The rapid reactions of nitrosoarenes with cellular SH groups have proved to be main metabolic conversions during detoxication. Interactions of the phenacetin metabolite 4-nitrosophenetole with glutathione have been investigated in detail during the last years, revealing a complex pattern of products depending on the stoichiometry of the reactants and reaction conditions. Eight metabolites have been identified hitherto, and the present work extends this medley by six additional products. Three metastable sulfenamides, 4-ethoxy-2,N-bis(glutathion-S-yl)-aniline, N4-(glutathion-S-yl)-4-amino-4'-ethoxydiphenylamine, and N-(glutathion-S-yl)-4-aminophenol, as well as the N-sulfenylquinonimine N-(glutathion-S-yl)-1,4-benzoquinonimine were characterized by chemical reactivity, chromatographic behavior, UV/vis absorption, 1H NMR, and FAB-MS data. The structure of the sulfenamide 2,N4-bis(glutathion-S-yl)-4-amino-4'-ethoxydiphenylamine could not be proved unequivocally, but is strongly suggested due to the chemical reactivity, chromatographic behavior, and UV/vis absorption of the compound. Finally, traces of 4-aminophenol were detected. A reaction scheme is presented explaining the formation of all identified metabolites via a central sulfenamide cation. Molecular orbital calculations for this sulfenamide cation have been performed, corroborating the proposed reaction mechanisms on the basis of Klopman's generalized perturbation theory.

Identification of a Novel Glutathione Conjugate of Flutamide in Incubations with Human Liver Microsomes

“…Several synthetic routes to sulfenamides have been developed over the years; however, information on the enzyme-catalyzed formation of these derivatives is relatively sparse. Mulder et al (1984) and Gallemann et al (1998) have previously reported the formation of a sulfenamide derivative of GSH. This conjugate was formed by reaction of 4-nitrosophenetole, derived from the oxidative metabolism of phenacetin via N-hydroxy-p-phenetidine, and GSH (Mulder et al, 1984;Gallemann et al, 1998).…”

“…Mulder et al (1984) and Gallemann et al (1998) have previously reported the formation of a sulfenamide derivative of GSH. This conjugate was formed by reaction of 4-nitrosophenetole, derived from the oxidative metabolism of phenacetin via N-hydroxy-p-phenetidine, and GSH (Mulder et al, 1984;Gallemann et al, 1998). However, the formation of N-acylsulfenamide, similar to the one described in this report, is not known.…”

Formation of 4,4-Dialkoxycyclohexa-2,5-dienone N-(Thiol-S-yl)imine during Reaction of 4-Alkoxynitrosobenzenes with Thiols in Alcoholic Solvents

“…GSO-NHPt: m / z 459 (100%, [M+H] + ), 322 (45%, [GSO] + ). GS-NHPt: m / z 443 (100%, [M+H] + ), 306 (37%, [GS] + ) ( , ). The presumed Et/Me-ketal eluting immediately in front of the sulfenamide GS-NHPt (Figure b) was detected by its UV absorption at 340 nm.…”

“…The scarce results reported hitherto on the reactivity of sulfenamide cations indicate the ring positions to react primarily with soft nucleophiles ( , ). The only reaction with a hard nucleophile, solvent water, is reported in the preceding paper ().…”

“…During the investigations of the underlying reaction mechanisms, a variety of observations pointed to the intermediate generation of an N-sulfenylnitrenium ion (also termed "sulfenamide cation"). Major hints at the occurrence of this reactive species came from kinetic investigations of nitrosoarene/ GSH interactions (2), and from detailed studies of the metabolic pattern observed during the reaction of the phenacetin metabolite 4-nitrosophenetole (NOPt 1 ) with GSH (3)(4)(5)(6)(7)(8). The multiplicity of products has been most plausibly explained as resulting from interactions of the resonance-stabilized sulfenamide cation with various nucleophiles.…”